The invention relates to a device for switching electrical contacts adapted to electrically transmit automatic aperture control and manual aperture control switching data from a photographing lens in an interchangeable lens type camera to the camera body side.
Two techniques for carrying out automatic exposure control in a camera are a "shutter speed priority automatic exposure" system (or EE system) in which the shutter speed is determined manually by the photographer and the aperture is automatically adjusted in accordance with the shutter speed thus determined, and an "aperture priority automatic exposure" (ES system) in which first the aperture value is manually determined by the photographer and the shutter speed is automatically adjusted in accordance with the aperture value thus determined.
A photographing lens which can be used with both of the two above-described systems has an automatic aperture mechanism for allowing the camera body to automatically control the lens opening in the EE mode and a manual aperture mechanism which allows the photographer to manually determine the lens opening in the ES mode.
Heretofore, the automatic and manual exposure control switching signal of a photographing lens has most often been mechanically transmitted. However, mechanically transmitting the switching signal with high accuracy as described above is disadvantageous in that the required mechanism is intricate and large in size which makes the lens expensive.
Furthermore, a technique has been proposed in the art in which data as to a present aperture opening and the minimum aperture value of a photographing lens and the aforementioned automatic and manual aperture control switching signal are transmitted as electrical signals from the lens side to the camera body side. To do this, a change-over switch for producing the automatic and manual aperture control switching signal in the lens barrel is provided and the signal produced thereby is applied to an electrical contact on the lens mount through a lead wire. However, in this case it is necessary to provide a space for the lead wire in the lens barrel. Therefore, such a change-over switch cannot be provided in a small and light photographing lens.